Plans for Measurement of Parity Nonconservation in Elastic Scattering of Polarized Electrons by Nuclei at the Bates Linear Accelerator Center

摘要

We are planning to measure the parity-violating asymmetry A = (sigma exp + -sigma e)/(sigma exp + +sigma exp - ) for the differential elastic scattering of positive (+) and negative (-) helicity electrons from exp 12 C nuclei. This asymmetry determines the axial-electron isoscalar coupling constant ( gamma in Sakurai's notation) between electrons and quarks. Since carbon is spinless and isoscalar, it has only one form factor, which cancels in the asymmetry. The interpretation of the result is consequently free of ambiguities arising from the structure of the nucleus. The experiment will take place at the Bates Linear Accelerator Center with a 250 MeV electron beam and at a Q exp 2 of 0.023 (GeV/c) exp 2 . Polarized electrons will be provided by a photoemission solid state source.